This invention relates to a colorimeter for measuring the color of a test sample such as teeth or the like, and more particularly relates to a colorimeter having a digital display with continuous update for indicating the color density values of the test sample. Morover, this invention is directed to a method of predetermining the color of a mixture of two porcelains for use in automating restorative dentistry, leading also to a new method for fabricating an artificial tooth, cap, filling or the like.
The steps or procedures usually followed in conventional restorative dentistry are quite subjective and usually include visual comparisons by the dentist and laboratory technician between a reference tooth, such as the tooth to be replaced, capped or filled and/or those adjacent the same, sample artificial teeth on a shade guide, and constructed artificial teeth, caps or fillings. Such conventional color matching techniques are relatively inaccurate and often lead to improper matching between the restoration and the surrounding teeth, for example, due to the subjectivity in the selection procesess and errors therein and to the non-uniformity of shade guides. Moreover, a dentist may draw a map representing colors of different portions of a tooth to be replaced with reference to the shades of several sample teeth on the shade guide, and the subjectivity involved in selecting a matching color for each portion further compounds the inaccuracies of the conventional restoration process.
One prior art device intended to facilitate visual comparison of tooth color with respective colors on a color shade guide is disclosed in U.S. Pat. No. 3,436,157. Although such patented device may increase the accuracy of the visual comparisons made in restorative dentistry, the resultant determinations are still subject to the visual perceptions of the operator.
The conventional method for manufacturing artificial teeth in accordance with given color and opacity data taken from a shade guide comprises the steps of hand sculpting the tooth from certain selected porcelains of respective colors and opacity, and then firing the tooth in a furnace. Such method is subject to the inaccuracies both in the selection of appropriately colored porcelains with which to build the tooth, such selection usually being trial and error approximations, and in the visual perceptions in comparing the constructed artificial tooth restoration relative to the data of the selected color or colors of the shade guide.